Introduction to GIS

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					    Introduction to GIS



Definition and Components of GIS
                               Lecture Outline

• What is GIS?
• Evolution of GIS
• Elements of A GIS
• The scope of GIS
• Data Structures
Definition and Components of GIS
G eographic
I nformation
S ystem
Definition and Components of GIS
                              GEOGRAPHIC
• GEO - physical aspects
      - socio-demographic aspects
      - artificial aspects




     *all with fixed locations (coordinates)


Definition and Components of GIS
                              GEOGRAPHIC
• GRAPHIC - does not refer to graphic
            representations like maps
          - refers to description of the
            earth and what is upon it
          - described in a digital model (3D)
            which allows visualization at any
            possible point of view
          - presentation of processed data in
            the form of one or more maps
Definition and Components of GIS
                            INFORMATION
•    "communication of knowledge"
•    a GIS provides information
•    by itself, a GIS does not contain information
•    a GIS makes information - by processing data
     already entered



Definition and Components of GIS
                                   SYSTEM
• Regularly interacting group of items
  forming a unified whole.




Definition and Components of GIS
                                   GIS
     A computer system for
     capturing, managing,
     integrating, manipulating,
     analyzing and displaying
     data spatially referenced.
                                         -Donnell & Kemp, 1995
Definition and Components of GIS
              EVOLUTION OF A GIS
    -evolved from different fields in which development has
    led to the GIS as we now know it.

•    cartography (high quality drafting)
•    CAD / computer graphics
•    surveying
•    remote sensing
•    computer technology (made it affordable)


Definition and Components of GIS
        Geographical data describes
        objects from the real world...
• position w/ respect to a known coordinate
  system
• their attributes (e.g. pH, color, cost, etc.)
• their spatial interrelations w/ each other
  (topological relations), which describe how
  they are linked or how one can travel
  between them

Definition and Components of GIS
  Items in a GIS are classified into
      separate components….

 •degree of hardness or
  tangibility
 •position in the data
  flow
Definition and Components of GIS
                     According to
                 Hardness or Tangibility
• hardware
• software
• orgware


Definition and Components of GIS
                                   HARDWARE
• micro pc - at least a 486DX with minimum
  16 megabytes ram, 1 GB hard disk with
  color monitor (at least 256 colors)
• scanner and /or digitizer
• inkjet printer and/or plotter
• any large data storage device


Definition and Components of GIS
                                   SOFTWARE
•    IDRISI                            •   MAPINFO
•    ILWIS                             •   OZ-GIS
•    ARCVIEW                           •   ER MAPPER
•    PC ARCINFO                        •   GRASS
                                       •   ATLAS




Definition and Components of GIS
                                   ORGWARE
• organization about the use of hardware and
  software
• man, their methods and organization
• “education and training” of staff at all levels




Definition and Components of GIS
            According to
      POSITION IN DATA FLOW
• input
• storage /management
• processing, manipulation and
  analysis
• output
Definition and Components of GIS
              DATA…DATA…DATA
• valid output needs a valid input - expensive
• collect only needed data but due to expense
  in collection, the data should also be
  multipurpose, ie., it can still be used by
  unrelated independent users
• data exchange - standards are needed
• data quality - the potential error should be
  measurable
Definition and Components of GIS
     DATA COST vs DATA QUALITY
DATA COST




            0
            0%                     DATA QUALITY   100%


Definition and Components of GIS
 3 components of geographic data
• the phenomenon being reported (physical
  dimension or class) e.g., live coral cover,
  height of forest canopy, population of a
  settlement, width of a road
• spatial component - represented on a map as
  either a point, line or area.
• time - not stated explicitly, but often critical

Definition and Components of GIS
                                   DATA INPUT
• involves also converting data (analog to
  digital)
• typically the major bottleneck
• GIGO, so checking for inaccuracies is very
  important
• input methods and standards must be
  considered first before data entry

Definition and Components of GIS
              DATA MANAGEMENT
• storing and retrieving data
• method implemented affects the efficiency
  of the system
• also involves organization of data - its
  structure and relationships determine how
  data is accessed and the speed of the
  retrieval

Definition and Components of GIS
                        DATA ANALYSIS
• determines the information that can be
  generated
• introduction of a GIS will not only
  automate, it will also change the way an
  organization works




Definition and Components of GIS
                            DATA OUTPUT

• maps
• tables
• text


Definition and Components of GIS
GIS Planning
  Process




 Definition and Components of GIS
                              SCOPE OF GIS
                              (a specific purpose)

• spatial analysis
• spatial planning
• implementation of plans
• spatial management

Definition and Components of GIS
                  SPATIAL ANALYSIS
• starts with a description of the situation at a
  given moment (point-in-time measurement
  which may not be sufficient particularly if
  the purpose is to gain insight as to how the
  situation develops in the future)




Definition and Components of GIS
                   SPATIAL ANALYSIS
                    (a “simplistic” case)
• assume coral reef susceptibility to man-induced
  destruction is determined by:
   – availability of materials for blast fishing
   – population density of dynamite fishermen
• it is the relationships between these factors that
  determines reef areas most susceptible to man-induced
  destruction



 Definition and Components of GIS
                                   The Problem

 Find coral reef areas in
 Cebu that have the lowest
 potential for success in
 coral reef conservation.

Definition and Components of GIS
                  What data do we need?
• coral coverage - map of coral coverage (MAP 1)
• availability of materials for blast fishing - map
  showing locations of large mango plantations
  (MAP 2)
• density of dynamite fishermen - map showing
  population densities of dynamite fishers in coastal
  areas (MAP 3)




Definition and Components of GIS
       How do we analyze the data?
• Map 1 - show areas with >50% live coral
  coverage
• Map 2 - show coastal areas that are near a
  large mango plantation.
• Map 3 - show coastal areas that have high
  population densities for bad fishermen



Definition and Components of GIS
MAP 1




                                   Areas with good coral reefs….

Definition and Components of GIS
    MAP 2




                                   coastal areas near large mango plantations….

Definition and Components of GIS
MAP 3




                            Areas with high densities of bad fishermen
Definition and Components of GIS
            The analysis produces…...
• MAP 4 - intersection areas in all the 3 maps
  produced earlier will show the areas that are:
       – having coral coverages > 50%
       – near dynamite sources
       – near areas with high density of bad fishermen


• these are unsuitable areas for reef reserves…

Definition and Components of GIS
  MAP 5




                                   Areas unsuitable for reef reserves
                                   Areas suitable for reef reserves



Definition and Components of GIS
                 SPATIAL PLANNING
• as a result of the analysis one can judge
  whether an area is suitable (high possibility
  of success) for the establishment of a
  marine sanctuary or not……planning
• the design of the plan also specifies where
  in the environment what interventions
  should occur - an outline of the future
  situation
Definition and Components of GIS
   IMPLEMENTATION OF THE
          PLANS
• plans are executed
• not anymore controlled by the GIS but can
  be monitored by it….. which leads us to the
  management aspect




Definition and Components of GIS
        SPATIAL MANAGEMENT
• monitoring…. wherein changes are
  recorded and attention is paid that no major
  disturbances occur
• degree of destruction is closely watched




Definition and Components of GIS
                  DATA STRUCTURES
• data always refers to a location on the
  surface of the earth expressed in a local or
  global co-ordinate system
• data has to be digitally stored for a
  computer to be able to read it




Definition and Components of GIS
                        WHERE & WHAT
• description of the world can be done in
  geographical terms (where are the
  objects),
• or in thematic expressions (what are the
  objects)
     *a meaningful description of the real world in its spatial
     manifestation always contains both.



Definition and Components of GIS
      DISTINCTION BETWEEN
     SEMANTICS AND SYNTAX
• content (what?)                  • convention (how?)
• the meaning                      • the format
• what it represents in            • how it is stored in the
  reality                            computer




Definition and Components of GIS
“Ich mag GIS”
“Ganahan ko sa GIS”
“Four added to five makes ten”

“Fayb added to fayb makes ten”

Definition and Components of GIS
    2 MAJOR DATA SYNTAXES

                       RASTER or GRID

                                     &

                                   VECTOR

Definition and Components of GIS
                         RASTER or GRID
                                   • a “grid” of a uniform
                                     pattern is put over
                                     area to be described
                                   • to each element a
                                     value is attributed
                                   • with a regular
                                     structure - position
                                     of each element can
                                     be defined in relation
                                     to the rest
Definition and Components of GIS
                                   VECTOR
                                       • structure points are
                                         recorded in co-
                                         ordinates and these are
                                         connected to lines (the
                                         vectors)
                                       • a number of vectors
                                         can be joined to form
                                         polygons (areas)
                                       • considers objects


Definition and Components of GIS
                                   3 object types
 • point - geometric description only refers to the
   position of the object by a pair of coordinates
   (x, y); used for trees, posts etc.
 • line - geometrically described by recording the
   coordinates of a series of points and the
   sequence in which these points should be linked
   (1D; eg., roads, canals, rivers)
 • polygon - a line with the same start and end,
   usually refers to an enclosed region (2D; eg.,
   lakes, ponds, farm plots)
Definition and Components of GIS
         A Line in…………………..
             raster                vector




Definition and Components of GIS
row = 1
column = 1
data = 1

row = 2
column = 1
data = 0



row = 3
column = 3
data = 1


a raster line……..
  Definition and Components of GIS
     start position
        (x1, y1)


                                                   may also be
                                                   a function




                                    end position
a vector line …….                     (x2, y2)
 Definition and Components of GIS
                                    RASTER vs VECTOR
• FILE SIZE                          • larger   • smaller

• SPEED                              • faster   • slower

• LINKING                            • easier   • A bit more
  DATA                                            difficult

• ACCURACY                           • ?        • ?

 Definition and Components of GIS
    VECTOR overlaying RASTER




Definition and Components of GIS

				
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